After some web searching I found these two resources on PL/SQL. Of course there are many others, but these two seem fairly good without being overly complicated.
Using Oracle PL/SQL from Stanford University
PL/SQL Reference & Tutorial from Elliot Spencer’s web site
While neither of these sites display the polish of a site like w3schools.com they both have great, well organized information.
For more of my favorite Oracle resources, check out my previous article on Oracle Web Resources